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Inorganic Chemistry: Period 3 Elements

The document describes reactions of Period 3 elements with oxygen, water, and the acid-base properties of their oxides. It introduces the Period 3 elements sodium to argon and their properties like atomic radius and reactivity. Sodium, magnesium, and aluminum react with oxygen to form ionic oxides while silicon reacts slowly to form silicon dioxide with a giant covalent structure. Sodium reacts vigorously with water while magnesium does not but reacts with steam. Chlorine reacts with water to form hydrochloric and hypochlorous acids. The oxides vary from basic to acidic depending on their structure and ability to bond or dissolve in water and acids. Aluminum oxide is amphoteric due to its

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Aidah Amir
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169 views5 pages

Inorganic Chemistry: Period 3 Elements

The document describes reactions of Period 3 elements with oxygen, water, and the acid-base properties of their oxides. It introduces the Period 3 elements sodium to argon and their properties like atomic radius and reactivity. Sodium, magnesium, and aluminum react with oxygen to form ionic oxides while silicon reacts slowly to form silicon dioxide with a giant covalent structure. Sodium reacts vigorously with water while magnesium does not but reacts with steam. Chlorine reacts with water to form hydrochloric and hypochlorous acids. The oxides vary from basic to acidic depending on their structure and ability to bond or dissolve in water and acids. Aluminum oxide is amphoteric due to its

Uploaded by

Aidah Amir
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Module 1

Inorganic
Chemistry
Period 3 Elements
Ung Hie Huong

LEARNING OUTCOMES:
Students should be able to:
Describe the reactions of Period 3 elements with oxygen
Interpret the ability of elements to act as oxidising and reducing agents
Describe the reactions of Period 3 elements with water
Describe and explain the acid-base properties of oxides of Period 3 elements

1.1

Introduction to Period 3 elements

Group
Element

13

14

15

16

17

18

Na

Mg

Al

Si

Cl

Ar

Atomic radius

Decreases

Entalphy of fusion

Decreases

Entalphy of
vaporisation

Decreases

First ionisation
energy

Increases

Electronegativity

Increases

Type of element
Electrical
conductivity
Type of bond

Metal

Metalloid

Nonmetal

Conductor

Semi
conductor

Nonconductor

Metallic bond

Physical state of
element at r.t.p.

Covalent bond
Solid

Atomic radius (coded by ball size)

Gas

1.2

Reaction of Period 3 elements with oxygen

Group
Element
+

O2

13

14

15

16

17

18

Na

Mg

Al

Si

Cl

Ar

Na2O

MgO

Al2O3

SiO2

P4O6/ P4O10
(In excess O2)

Element
Sodium, Na

Magnesium,
Mg

Aluminium,
Al

Silicon, Si

Phosphorus,
P

Sulphur, S

Reaction with oxygen (Observation/ Equation)


Observation

Burns in oxygen with a bright yellow flame.


A white ionic solid, sodium oxide (Na2O) is formed.

Equation

4Na(s)

Observation

Burns in oxygen with a brilliant white flame.


A white ionic solid, magnesium oxide (MgO) is formed.

Equation

2Mg(s)

Observation

Burns in oxygen with a brilliant white flame.


A white ionic solid, aluminium oxide (Al2O3) is formed.

Equation

4Al(s)

Observation

Reacts slowly with oxygen.


White solid, silicon dioxide (SiO2) is formed.
Note: Silicon dioxide or silicon(IV) oxide has a giant
covalent structure.

Equation

Si(s)

Observation

White phosphorus bursts into flames spontaneously when


exposed to air.
In limited amount of air: Phosphorus trioxide, P4O6, is
formed.
In excess air: Phosphorus pentoxide, P4O10, is formed.

Equation

In limited amount of air: P4(s) + 3O2(g)


P4O6(s)
In excess air: P4(s) + 5O2(g)
P4O10(s)

Observation

Sulphur
Sulphur
Sulphur
trioxide,

Equation

S(s) + O2(g)
2SO2(g) + O2(g)

+ O2(g)

2Na2O(s)
White

+ O2(g)

+ 3O2(g)

+ O2(g)

2MgO(s)
White

2Al2O3(s)
White

SiO2(s)
White

burns with a blue flame.


dioxide, SO2 (colourless gas) is formed.
dioxide, SO2 can be oxidised slowly to sulphur
SO3.

SO2(g)
2SO3(g)

1.3

Reaction of Period 3 elements with water

Group
Element
+

H2O

13

14

15

16

17

18

Na

Mg

Al

Si

Cl

Ar

NaOH

MgO

HCl + HOCl

Element
Sodium, Na

Magnesium,
Mg

Chlorine,
Cl2

Reaction with water (Observation/ Equation)


Observation

Reacts vigorously with water.


Forms an alkaline solution (turns pink litmus solution to
blue) & hydrogen gas (gives a pop sound with burning
splinter)

Equation

2Na(s)

Observation

Does not react with water.


React with steam.
Forms magnesium oxide (MgO) and hydrogen gas.

Equation

Mg(s)

Observation

Reacts slowly with water.


Forms acidic solution, hydrochloric acid and chloric(I) acid.
Blue litmus solution turns red, then bleached/ decolourised.

Equation

Cl2(g)

+ 2H2O(l)

+ H2O(g)

+ H2O(l)

2NaOH(aq)
Alkali

MgO(s)

HCl(aq)

+ H2(g)

+ H2(g)

+ HOCl(aq)
Bleaching agent

ALL noble gases (Group 18 elements) are inert


and unreactive.
This is due to their duplet and octet valence
electron configuration.
The valence orbitals are all fully filled &
stable.

1.4

Acid-base properties of oxides of the Period 3 elements

Group
Oxide
Oxidation number

1
Na2O

2
MgO

13
Al2O3

14
SiO2

+1

+2

+3

+4

Ionic-covalent

Giant covalent

Structure
Physical state (r.t.p.)
Acid-base property
+ Water

+ HCl

Ionic

Solid
Basic
Dissolves

Weakly Basic
Insoluble

Na2O + H2O
2NaOH

The lattice energy


that hold Mg2+ ions
and O2 ions
together is too high

Dissolves
Na2O + 2HCl
2NaCl + H2O

+ NaOH

Dissolves
MgO + 2HCl
MgCl2 + H2O

Amphoteric
Insoluble

Dissolves
Al2O3 + 6HCl
2AlCl3 + 3H2O
Dissolves
Al2O3 + 2NaOH
+ 3H2O
2NaAl(OH)4
Sodium aluminate

Electric conductivity

Acidic
Insoluble

Electrolyte (in molten & aqueous state)

15
P4O6
P4O10
+3
+5
Liquid
Solid
Acidic
Dissolves

16
SO2
SO3
+4
+6
Simple covalent
Gas
Gas
Acidic
Dissolves

17
Cl2O
Cl2O7
+1
+7
Gas
Liquid
Acidic
Dissolves

P4O6 + 6H2O
4H3PO3

SO2 + H2O
H2SO3

Cl2O + H2O
2HClO

P4O10 + 6H2O
4H3PO4

SO3 + H2O
H2SO4

Cl2O7 + H2O
2HClO4

Dissolves in
conc. NaOH
SiO2 + 2NaOH
Na2SiO3 +
H2O

Why is aluminium oxide amphoteric?


Because it is an ionic compound with partial covalent character.

Non-electrolyte

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